1. Field of the Invention
This invention relates to the utilization of natural gas, having a relatively high content of carbon dioxide in admixture with methane, to produce liquid fuel. In its preferred embodiment, the invention is also concerned with supply of a product gas stream rich in carbon dioxide and having reduced methane content as compared with the natural gas processed. Such product gas stream is utilized in tertiary methods of recovery of liquid petroleum from underground reservoirs which have been depleted to the extent viable by primary and secondary recovery methods.
2. Description of the Prior Art
The natural gases of interest in the process of this invention have previously been regarded as having no significant commercial value. Natural gas containing mixtures of carbon dioxide and methane in substantially equal volumes, and those containing a major proportion of methane, have been processed to separate the methane from the carbon dioxide and thus provide fuel gas of pipeline quality. However, it has been considered economically unrealistic to produce natural gas from extensive known reservoirs in which the gas contains a major proportion of carbon dioxide. The cost of the separation of the methane content of the gas from these reservoirs is too great, in comparison with the value of the recovered methane, to justify the construction and operation of separation facilities. Assuming a use for the carbon dioxide in tertiary recovery at petroleum reservoirs within a distance which can justify transporting the gas, such mixtures are unsuitable because of their content of methane which is known to inhibit solubility of carbon dioxide in petroleum.
In providing a combination of process steps which yield valuable products from natural gas previously considered valueless, the invention described herein utilizes known technology for:
(1) GENERATING A SYNTHESIS GAS OF CARBON MONOXIDE AND HYDROGEN PRIMARILY FROM THE REACTION OF METHANE AND WATER;
(2) SYNTHESIS OF METHANOL OR LIQUID HYDROCARBONS BY REACTION OF CARBON OXIDES AND HYDROGEN; AND
(3) TERTIARY RECOVERY OF PETROLEUM BY INJECTION OF CARBON DIOXIDE, WHICH CONTAINS LITTLE METHANE, INTO AN UNDERGROUND RESERVOIR, IT BEING KNOWN THAT METHANE REDUCES THE SOLUBILITY OF CARBON DIOXIDE IN PETROLEUM.